1. Field of the Invention
The present invention relates to an apparatus and method for testing the concentration of a particular gas from a source using a length of stain detection device, i.e. a Drager tube, and more particularly to the storing of the tested gas in the same apparatus for later analysis and the flaring of the gas for disposal.
2. Description of Related Art
It is a common practice in chemical plants to test for hazardous substances such as poisonous hydrogen sulfide gas in samples taken from process lines, petroleum storage tanks and other confined spaces. For sampling, typically five gas detection apparatus are used to collect separate gas samples from the same source. Of these five, two are run through a Drager tube, discussed below, to determine the concentration of the particular gas tested. The other three samples are saved in the apparatus for up to three to five years for further analysis. A shortcoming of this method of sampling, however, is the great expense incurred because of the necessity of purchasing five gas detection apparatus for each test. The expense would be sharply reduced if a single gas detection apparatus both ran the gas sample though the Drager tube and stored the gas after testing.
A gas detection apparatus that is representative of the type used for the above sampling is disclosed by U.S. Pat. No. 5,098,847, entitled METHOD AND APPARATUS FOR PORTABLE TESTING OF PRODUCTS FROM PROCESSING COLUMN issued to Welker Mar. 24, 1992. The '847 patent teaches a portable test apparatus in which the gas sample is collected within a cylinder defining a chamber and having a movable piston coupled to a piston rod therein. A passage that is selectively vented to the atmosphere by means of a first valve is positioned behind the piston rod, such that when the first valve is opened, the piston is able to move within the chamber. The chamber is connected to a process line with a second valve positioned therebetween, which when opened fills the cylinder with the gas from the process line while displacing the piston back within the chamber. When the chamber is full, a third valve leading to a valve connection port with a Drager tube is opened. A Drager tube is a length of stain detection device containing a reagent specifically sensitive to a particular vapor or gas. When in use, the hermetically-sealed two ends of the Drager tube are broken and one end is placed in selective communication with the gas to be sampled, in this case the valve connection port. With the third valve open, the piston rod is manually pushed forward, thereby forcing the gas sample through the Drager tube and out into the atmosphere.
Due to an increased awareness of the environmental considerations associated with the emitting of gaseous fluids and other toxins into the atmosphere, the government is now requiring companies to flare all potentially toxic gaseous substances, such as those tested with gas detection systems in chemical plants, instead of merely venting the hazardous substances to the atmosphere. As a result, while there are readily available apparatus for testing the concentration of a particular gas in a sample, such as the one described above, there has yet to be developed an apparatus which provides a system for discharging the gas sample to a flare line as opposed to the atmosphere.
With the above considerations in mind, it is an object of the present invention to eliminate the great expense of sampling incurred by purchasing separate gas detection apparatus for the testing and storing of a gas sample by providing a gas detection apparatus which extracts a gas sample from a gas source, tests the gas sample through a Drager tube, and then stores the gas sample for later analysis.
It is a further object of the present invention to provide an apparatus which vents a gas sample to a flare line as opposed to the atmosphere.